1. Field of the Invention
This invention relates to refrigerant recovery systems. More specifically, it relates to an arrangement for recovery of refrigerant from a refrigeration system wherein all controls and mode switching are done manually by the operator.
2. Description of the Prior Art
A wide variety of mechanical refrigeration systems are currently in use in a wide variety of applications. These applications include domestic refrigeration, commercial refrigeration, air conditioning, dehumidifying, food freezing, cooling and manufacturing processes, and numerous other applications. The vast majority of mechanical refrigeration systems operate according to similar, well known principals, employing a closed-loop fluid circuit through which a refrigerant flows. A number of saturated fluorocarbon compounds and azeotropes are commonly used as refrigerants in refrigeration systems. Representative of these refrigerants are R-12, R-22, R-500 and R-502.
Those familiar with mechanical refrigeration systems will recognize that such systems periodically require service. Such service may include removal, of, and replacement or repair of, a component of the system. Further during normal system operation the refrigerant can become contaminated by foreign matter within the refrigeration circuit, or by excess moisture in the system. The presence of excess moisture can cause ice formation in the expansion valves and capillary tubes, corrosion of metal, copper plating and chemical damage to insulation in hermetic compressors. Acid can be present due to motor burn out which is caused by overheating of the refrigerant. Such burn outs can be temporary or localized in nature as in the case of a friction producing chip which produces a local hot spot which overheats the refrigerant. The main acid of concern is HCL but other acids and contaminants can be produced as the decomposition products of oil, insulation, varnish, gaskets and adhesives. Such contamination may lead to component failure or it may be desirable to change the refrigerant to improve the operating efficiency of the system.
When servicing a refrigeration system it has been the practice for the refrigerant to be vented into the atmosphere, before the apparatus is serviced and repaired. The circuit is then evacuated by a vacuum pump, which vents additional refrigerant to the atmosphere, and recharged with new refrigerant. This procedure has now become unacceptable for environmental reasons, specifically, it is believed that the release of such fluorocarbons depletes the concentration of ozone in the atmosphere. This depletion of the ozone layer is believed to adversely impact the environment and human health. Further, the cost of refrigerant is now becoming an important factor with respect to service cost, and such a waste of refrigerant, which could be recovered, purified and reused, is no longer acceptable.
To avoid release of fluorocarbons into the atmosphere, devices have been provided that are designed to recover the refrigerant from refrigeration systems. The devices often include means for processing the refrigerants so recovered so that the refrigerant may be reused. Representative examples of such devices are shown in the following U.S. Pat. Nos. 4,441,330 "Refrigerant Recovery And Recharging System" to Lower et al; 4,476,688 "Refrigerant Recovery And Purification System" to Goddard; 4,766,733 "Refrigerant Reclamation And Charging Unit" to Scuderi; 4,809,520 "Refrigerant Recovery And Purification System" to Manz et al; 4,862,699 "Method And Apparatus For Recovering, Purifying and Separating Refrigerant From Its Lubricant" to Lounis; 4,903,499 "Refrigerant Recovery System" to Merritt; and 4,942,741 "Refrigerant Recovery Device" to Hancock et al.
When most such systems are operating, a recovery compressor is used to withdraw the refrigerant from the unit being serviced. As the pressure in the service unit is drawn down, the pressure differential across the recovery compressor increases because the pressure on the suction side of the compressor becomes increasingly lower while the pressure on the discharge side of the compressor stays constant. High compressor pressure differentials can be destructive to compressor internal components because of the unacceptably high internal compressor temperatures which accompany them and the increased stresses on compressor bearing surfaces. Limitations on the pressure differentials or pressure ratio across the recovery compressors are thus necessary, such limitations, in turn can limit the percentage of the total charge of refrigerant contained within the unit being serviced that may be successfully recovered.
When using such recovery systems in servicing larger refrigeration systems it is particularly advantageous to have the capability of withdrawing refrigerant from the system in the liquid form and delivering it directly to a storage cylinder. The recovery of the refrigerant in liquid form, because of its much greater density, is obviously far quicker than recovery in the vapor state.
Commonly assigned U.S. application Ser. No. 07/612,642 entitled METHOD AND APPARATUS FOR RECOVERING AND PURIFYING REFRIGERANT INCLUDING LIQUID RECOVERY was filed on Nov. 13, 1990. This Application discloses a microprocessor controlled apparatus capable of both recovering and purifying refrigerant. The disclosed device is capable of withdrawing refrigerant in a liquid state directly from a refrigeration system being serviced and delivering the refrigerant to a storage cylinder. This system is also capable of cooling the refrigerant storage cylinder during the liquid recovery mode to lower the pressure and temperature of the storage cylinder below ambient temperature. The system is capable of automatically shifting from a liquid recovery mode to a vapor recovery mode when predetermined conditions in the recovery system are measured.
Commonly assigned U.S. application Ser. No. 07/816,002 entitled Manually Operated Refrigerant Recovery Apparatus was filed on Jan. 2, 1992 now U.S. Pat. No. 5,181,390. This application discloses a manually controlled refrigerant recovery apparatus. The system allows the manual control of the recovery apparatus to allow refrigerant withdrawn from a refrigeration system and transferred to a storage cylinder to be cooled to lower the pressure and temperature of the storage cylinder below ambient temperature. The apparatus indicates to an operator when to manually take the steps necessary to shift from a liquid recovery mode to a vapor recovery mode.
Operation of the system of this application requires a relatively high level of skill of the operator in order to operate the proper manually operated switches and valves in order to effect the desired evacuation of the refrigeration system being serviced.
Further, the control system of that application does not afford protection to the recovery systems compressor that is provided by the pressure ratio sensing capability of the microprocessor of the above identified application Ser. No. 07/612,642.